Manual and General Information regarding earth construction, its types, and their application

1. EARTH
CONSTRUCTION
Reference
Manual
-Sayam
Mulani

2. Ancient Great Mosque of Djenne in Mali
Introduction
Earth structures are largely made from soil with added materials, compressed or baked to add strength.
Soil is economical and has low environmental material.
Earth structure materials may be as simple as mud, or mud mixed with straw to make cob.
Sturdy dwellings may be also built from sod or turf.
Soil may be stabilized by the addition of lime or cement, and may be compacted into rammed earth.
Construction is faster with pre-formed adobe or mudbricks, compressed earth blocks, earthbags or fired clay bricks.
Hikma Mosque, Dandaji, Niger- Mariam Kamara

3. Soil
Soil particles include sand, silt and clay. Even a small proportion of clay affects the physical properties of the soil.
Loam is a mix of sand, silt and clay in which none predominates. Soils are given different names depending on the
relative proportions of sand, silt and clay such as "Silt Loam", "Clay Loam" and "Silty Clay". Loam construction referred
to as adobe construction when it uses unfired clay bricks, is an ancient building technology. It was used in the early
civilizations of the Mediterranean, Egypt and Mesopotamia, in the Indus, Ganges and Yellow river valleys,
in Central and South America.
It minimizes use of fossil fuels and pollution, particularly carbon dioxide, during manufacture, and creates a
comfortable living environment through the high mass and high absorption of the material. The two main technologies
are stamped or rammed earth, clay or loam, and adobe, typically using sun-dried bricks made of a mud and straw
mixture.
Ancient structures of Indus Valley Civilization

4. Soil Composition
Source:
• Mud required for building can be from the plot itself.
• The soil is collected after depth of 60cms only.
• As the top layer is full of organic matter, it isn’t used.
• Below it is sand and clay which are dug out in heaps.
• Do not use hard rock.
• Top should be replaced after excavating.
Soil Type:
• Gravel: Small pieces of stone varying from the size of a
pea to that of an egg. Alone of no use for mud wall
building as the tiny lumps of stone cannot bind together.
• Sand: Similar small pieces of stone (usually quartz),
which are small but each grain, is visible to the eye.
Alone is of no use but if mixed with clay, it is the ideal
mud wall building soil.
• Silt: The same as sand except that it is so fine that you
cannot see individual grains. By itself is also no good for
building walls. It will hold together but is not strong.
Furthermore, it will not compact so it is also of no use
for pressed blocks or rammed earthwork.
• Clay: Soils that stick when wet – but very hard when
completely dry. Can be rammed or compressed but in
drying out they often shrink. During the monsoon they
get damp and expand again and crack form.
• Organic Soil: Soil mainly composed of rotting,
decomposing organic matters such as leaves, plants
and vegetable matter. It is spongy when wet, usually
smells of decaying matter, is dark in color and usually
damp. Are mainly useless for wall building.

5. Soil Stabilizers
There are two kinds of tests:
Field tests
• Colour tests
• Touch and smell test
• Biscuit test
• Hand wash test
• Cigar test
• Adhesion test
Lab tests
• Sieve test
• Sedimentation
test
When the available soil is not suitable enough for construction then the soil can be used by manipulating its
composition by adding suitable stabilizers.
Stabilizing enhances the given property of the soil type.
Increase Tensile and Shear strength.
Reduce shrinkage.
Indigenous Stabilizers-
• Straw
• Plant Juices
• Gum Arabic
• Sugar Or Molasses
• Cow Dung
• Animal Urine
• Tannic Acid
• Oil
Soil
Tests

6. Soil Tests
Colour test:
• Deep yellow, orange and red, ranging to deep
browns indicate iron content which is good as
building mud.
• Greyish or dull brown, ranging to dirty white
indicates more clay.
• Dull brown with slightly greenish colour indicates
organic soil.
Touch and Smell Test:
Procedure-
• Rub small quantity of dry soil on palm to feel its texture.
• Moisten the soil and rub again.
Interpretation-
• Soil that feels course when dry but sticky when wet
contains lumps of clay.
• Soil that feels course when dry but gritty when wet
contains sand.
• Soil that feels course when dry but little gritty when wet
contains silt.
• If the wet soil gives off musty smell then it contains
organic matter.

7. Soil Tests
Biscuit Test:
Procedure-
• Make a smooth paste from the soil removing all
gravel.
• Mould it into a biscuit of 3cm diameter and 1cm
height.
• Leave it to dry and observe for shrinkages or
cracks.
• Break the biscuit to noting how hard it is.
Interpretation-
• If biscuit cracks or leaves gap from the mould then it
contains more clay.
• If its very hard to break then soil contains more clay.
• If it breaks easily and can be crumpled between
finger then it has good sand-clay proportion.
• If breaks and reduce to powder then the soil has
more sand or silt.
Handwash Test:
Procedure-
• Play with wet soil till your hands get thoroughly dirty.
• Wash your hands to see how difficult it is to clean.
Interpretation-
• If hands get cleaned quickly, then soil contains more
sand.
• If it takes little time to clean and feels like flour then
soil contains more silt.
• If it feels soapy or slippery and takes time to clean
then soil contains more clay.

8. Soil Tests
Cigar Test:
Procedure-
• Make a smooth paste from the soil removing all
gravel.
• Roll it on palm to make a cigar.
• Slowly push it outside your palm.
• Measure the length at which it breaks.
Interpretation-
• Length< 5cm – too much sand.
• Length> 15cm – too much clay.
• Length between 5cm to 15cm – good mixture of
sand and clay.
Adhesion Test:
Procedure-
• Make ball out of wet soil.
• Pierce a knife into it and remove.
• Observer the knife after removing.
Interpretation-
• If little soil sticks on the knife then it has more silt.
• If lot of soil sticks on the knife then it has more clay.
• If the knife is clean after removal than the soil has
more sand.

9. Soil Tests
Sieve Test:
Procedure-
• Pass soil from series of standard sieves set on top
of on another with finest sieve at bottom.
• Observe the soil collected in each sieve.
Interpretation-
• Silt will be collected in lowermost sieve.
• Gravels will be collected on top.
• Sand and lumps of clay will be collected in
intermediate sieves
Sedimentation Test:
Procedure-
• Take a transparent cylindrical bottle or jar of 1Lt.
Capacity.
• Fill it with ¼ soil and ¾ water.
• Shake well and allow it to settle for 30 min.
Interpretation-
• Coarse gravels will be settled at bottom, followed by
sand, silt and clay on top.
• Measuring the layers will give us the approximate
proportions of each content.

10. Ancient Great Mosque of Djenne in Mali
Mud
Coursed mud construction is one of the oldest approaches to building walls. Moist mud is formed by hand to make the
base of a wall, and allowed to dry. More mud is added and allowed to dry to form successive courses until the wall is
complete. With puddled mud, a hand-made mud form is filled with wetter mud and allowed to dry.
Each course is about 460 to 610 mm thick and 460 to 610 mm high. Typically used for garden walls but not for house
construction because of concern about the strength of walls made in this way.
Another technique is to build a wood-frame house and to infill it with mud to provide insulation.
Hikma Mosque, Dandaji, Niger- Mariam Kamara

11. Cob Construction
Cob is a natural building material that includes clay, sand or small stones and an organic material such as straw.
Cob walls are usually built up in courses, have no mortar joints and need 30% or more clay in the soil lending itself to
organic shapes like curved walls, arches, niches, etc.
Cob can be used as in-fill in post-and-beam buildings for load bearing walls, and can bear up to two stories.
It is plastered inside and out with a mix of lime, soil and sand.
Cob is fireproof, and its thermal mass helps stabilize indoor temperatures. Due to its porous nature, cob is quite
resistant to weathering and can withstand long periods of rain without weakening.
Construction Process-
• With only a little water to form a very stiff mud, a large lump is molded into the shape of a huge elongated egg.
• The usual size is anything between 30 to 40-cm long and about 15-cm in dia.
• A row of these cobs of mud are laid neatly side-by-side somewhat pressed together.
• Then another row of cobs is laid on top.
• When three or four courses have been laid, the sides are smoothed over so that the holes and cracks disappear.
• Openings for doors, and windows can be solved by using temporary vertical planks or shuttering.
• Another very simple shuttering for openings is to use empty kerosene tins.

12. Adobe Construction
Preparing soil mix
Charging the forms
Kneading and leveling the blocks
Lilting the forms from freshly made
blocks.
Washing forms for next
cycle.
Mix soil with water in a sump
Transport prepared soil mix to multi-
forms.
Unstabilized block is turned on edge to dry
Blocks stacked after a month of curing.

13. Adobe Construction
Mudbricks or Adobe bricks are preformed modular masonry units of sun-dried mud
Construction with bricks avoids the delays while each course of puddled mud dries.
Adobe bricks are traditionally made from sand and clay mixed with water to a plastic consistency, with straw or grass
as a binder.
The mud is prepared, placed in wooden forms, tamped and leveled, and then turned out of the mold to dry for several
days. The bricks are then stood on end to air-cure for a month or more.
Since adobe surfaces are fragile, coatings are used to protect them. These coatings, periodically renewed, have
included mud plaster, lime plaster, whitewash or stucco. Since adobe surfaces are fragile, coatings are used to protect
them. These coatings, periodically renewed, have included mud plaster, lime plaster, whitewash or stucco.
made by laying the bricks with mud mortar, which swells and shrinks at the same rate as the bricks when wetted or
dried, heated or cooled.
Adobe structures are extremely durable and the material has a high thermal mass. However, structures made of adobe
are susceptible to earthquake damage if they lack proper reinforcement.
Two typical sizes of blocks that have been used are 5x10x20 inches (weight about 55 pounds) and 4x12x18 inches
(weight about 50 pounds).
Construction Process-
• Blocks shall be kept covered with air tight polythene sheets for first 48 hrs with relative humidity up to 100.
• Polythene sheets shall be removed after 48 hrs and the blocks shall be kept in shaded area like having enough air
circulation.
• Sprinkle water over blocks daily, as many times needed, during 28 days.
• Write date of production on block corner.
• Cover stacks top with coconut leaves or any other cover to avoid direct sunlight.
• Principle is that blocks shall not dry for 4weeks.
• Adobe brick walls require wood lintels and sills that serve as the head and base of the frame.

14. Wattle and Daub
Wattle and daub is an old building technique in which vines or smaller sticks are interwoven between upright poles, or
the timber forms a woven lattice and is plastered with earth mixture that usually consists of wet soil, clay, sand, animal
dung, and straw.
Wattle and daub is still found as the panels in timber-framed buildings. Generally the walls are not structural, and in
interior use the technique in the developed world was replaced by lath and plaster, and then by gypsum wallboard.
The wall can range from 150 to 200 mm in thickness and this makes the technique attractive for dividing interior
spaces with light walls.
This technique is also suited for a more experimental approach to Earth building. The latticework can have nearly any
shape. Together with the earth mix very firm "objects" up to 2 meters high can be built.
Construction Process-
• There bamboo and cane frame structure that supports the roof.
• Mud is plastered over this mesh of bamboo cane and straws
• Due to excessive rainfall the Wattle and Daub structures gets washed off.
• However, the mesh of cane or split bamboo remains intact and after the heavy rain is over the mud is plastered on
again.

15. Earthbag Construction
Earthbag construction is a natural building technique that has
evolved from historic military construction techniques for bunkers.
Local subsoil of almost any composition can be used, although an
adobe mix would be preferable.
The soil is moistened so it will compact into a stable structure when
packed into woven polypropylene or burlap sacks or tubes. Plastic
mesh is sometimes used. Polypropylene (pp) sacks are most
common, since they are durable when covered, cheap, and widely
available.
Earthbags may be used to make dome-shaped or vertical wall
buildings.
With soil stabilization they may also be used for retaining walls.
The structures built using this technique also employ vaults and
corbelled arches as well as domes to create sturdy shells.
Construction Process-
• Rows of woven bags are filled with available inorganic material.
• After the foundation is laid, each successive layer will have one
or more strands of barbed wire placed on top.
• The weight of this earth-filled bag pushes down on the barbed
wire strands, locking the bag in place on the row below.
• The bags are laid in courses, with barbed wire between each
course to prevent slipping. Each course is tamped after it is laid.
• The structure in pp bags is similar to adobe but more flexible.
• With mesh tubing the structure is like rammed earth.
• Barbed wires are placed between each layer and serve as both
reinforcements as well as mortar.

16. Shaped Earth Construction
Similar to how a potter shapes mud into pots, the shaped earth
technique directly shapes the plastic earth without a mold or formwork.
The three factors that play a key role in this method are the quality of the
soil, its preparation, and water consistency.
A great advantage of this method is the minimal usage of tools as well as
the labor force.
Shaped earth allows fluidity in architecture to a great extent and the few
limitations to this technique are understanding the soil quality as well as
controlling shrinkage once the structure dries.

17. Mortar
Stabilized Earth Mortar is best suited for masonry using
mud blocks.
Mud mortar shall be stabilized 1.5 times more than the
mud blocks.
Add course sand (0.2 to 2mm) to reduce shrinkage.
Prepare plastic mix rather than dry mix.
Ideal mix = soil suitable for mud block + 40% to 50% of
sand by weight + 7.5% cement.
Test the mortar before use
Procedure-
• Start with a mix of 1 vol. Cement + 6 vol. Soil + 6 vol.
Sand.
• Apply a layer of 1cm mortar on a block soaked in
water and let it dray in shade.
• Observe the mortar for cracks.
Interpretation-
• If cracks appear, reduce the soil and increase the
sand proportion.
1 cement + 5 soil + 7 sand.
• If mortar is too crumbly, increase the soil and reduce
the sand proportion.
1 cement + 7 soil + 5 sand
Treatment
1.Termites-
• Mud is the natural home of termites precautions have
to be taken to prevent their moving up into the walls
and eating wooden frames etc.
• A one-inch thick layer of mortar (one part of cement
to 3-parts of sand) can be laid all over the top of the
basement wall before building the mud walls above it.
This is helpful in keeping out both termites and damp.
• Even better is to construct an apron of burnt brick or
stone (or it can be rammed earth) all round the
building (to prevent damage to the walls by splashing,
of rain water) and this too can be plastered over with
a rich cement mortar.
• Any thin sheet metal may be laid over the basement
wall with a 3-inch downward projection before starting
to build the superstructure mud wall above. This
is expensive but very effective.
2.Water-
• The best way of protecting any wall from either rain or
sun is to have a good big overhang to your roof.
• The sloping, or pitched roof is better because the
walls need not be so high as for a flat roofed house.
• Provide trenches round the house to receive dripping
water and drain it away.

18. Compressed Earth
Brick
Compressed earth blocks (CEB) are usually made from subsoil compressed in a hand-operated or powered machine.
Manual machines can be a cost-effective solution for making uniform building blocks, while the more complex and
expensive motorized machines are less likely to be appropriate.
Although labor-intensive, CEB construction avoids the cost of buying and transporting materials.
Block-making machines may form blocks that have interlocking shapes to reduce the requirement for mortar.
The block may have holes or grooves so rods such as bamboo can be inserted to improve earthquake resistance.
Suitable earth must be used, with enough clay to hold the block together and resist erosion.
When the block has been made from stabilized earth, which contains cement, the concrete must be given perhaps three
weeks to cure. During this time the blocks should be stacked and kept from drying out by sprinkling water over them.
The blocks can be made raw or stabilized with cement or lime.
The addition of stabilizers allowed construction of higher and thinner walls that have great compressive strength and
water resistance.

19. Clay Roof Tiles
• Burnt clay tile roofs are only used for sloping roofs
between about 20° and 50° inclination of rafter, and
the tile shapes differ for each range of slope. The
rafter pitch is always steeper than the tile pitch.
• Clay tile production is a traditional village craft but
uniform shapes and qualities are difficult to achieve.
Mechanized plants produce good quality tiles, but at
higher costs or mobile presses with interchangeable
moulds for different tile shapes.
• Depending on the clay type and production method, a
major problem of clay tiles is the immense loss (in
India about 35 %) due to cracking and breakage. A
good remedy has been found in the use of ammonium
chloride as an admixture varying between 0.1 and 1.0
%, depending on the type of soil.
• Clay tiles are heavy, requiring a strong substructure
and closely spaced battens. Therefore, tile designs (eg
Mangalore tiles), which require wider spacing of
battens, are lighter and more economical. But
generally, the weight of the roof and loose connection
of tiles, make them susceptible to destruction in
earthquakes.
• Good quality tiles with good overlaps are perfectly
waterproof. The red colour, however, tends to absorb
solar radiation, so theta suspended ceiling may be
needed for indoor comfort.